In the manufacturing process of thin film transistor liquid crystal display (TFT-LCD), in particular to the manufacturing process of array substrate or color filter substrate, the lithography process is applied in many steps. In the lithography process, project the pattern of the mask to the photoresist on the substrate by exposing the substrate with the photoresist via the mask with design pattern and the ultraviolet light of the exposure machine. In the manufacturing process of thin film transistor liquid crystal display (TFT-LCD), completing the manufacturing of array substrate and color filter substrate is need to applying the lithography process in many steps.
However, in the practice of the manufacturing process, the exposure machine has many sets of lenses, for example, an existing Nikon exposure machine has a light path system consisting of six sets of lenses. There is the ultraviolet light of multiple sets of lenses irradiating on the same region of the mask in the practice, which means that the lights of different lenses irradiate on a light overlap region of the mask. Because it is hard to adjust the lights of different lenses to the best target position, and the light intensity of the light overlap region and the light intensity of the center region of the lens have variations, the photoresist pattern obtained by passing through the light overlap region and the needed photoresist pattern (target photoresist pattern) have variations on key size. In general, the light intensity of the light overlap region is weaker than the light intensity of the center region of the lens. If using a negative photoresist, the thickness of the obtained photoresist pattern will be thinner than the thickness of the target photoresist pattern, due to the amount of the exposure is not enough in the light overlap region. If using a positive photoresist, the thickness of the obtained photoresist pattern will be thicker than the thickness of the target photoresist pattern, due to the amount of the exposure is too much. Therefore, the lens mura phenomenon will happen, and the phenomenon easily makes the yield of the small-size panel with high resolution decrease.